1. Field of the Invention
This disclosure relates to the field of semiconductor device manufacturing, and in particular relates to a method of manufacturing a phase change semiconductor device and the phase change semiconductor device.
2. Description of the Related Art
A phase change material such as a chalcogenide can be subjected to a reversible phase change between a crystalline state and an amorphous state. When the phase change material is in a crystalline state, it has a lower resistivity; whereas when the phase change material is in an amorphous state, it has a higher resistivity.
Taking advantage of this property, a phase change material can be used to implement a phase change semiconductor device. One example of a phase change semiconductor device is a phase change memory. A phase change memory has excellent properties such as one-bit-alterability, nonvolatility, fast reading speed, no necessity to be erased separately etc., and thus is considered widely as one of the most promising candidates for advanced semiconductor processes.
FIG. 1 is a schematic diagram illustrating a basic structure of a phase change semiconductor device. As shown in FIG. 1, a phase change material layer 150 is formed in a via hole in an insulating layer 120 on a substrate 110, and the phase change material layer 150 is sandwiched between a top electrode 165 and a bottom electrode 115. In addition, FIGS. 2A and 2B illustrate structures obtained after forming the phase change material layer 150 and after performing a planarization process in a conventional phase change semiconductor device manufacturing process, respectively.
The present inventor has conducted in-depth investigation on the conventional phase change semiconductor device manufacturing process, and has found that the following problems exist.
When performing a planarization process after forming the phase change material layer 150 on the insulating layer 120 (see FIGS. 2A and 2B), the formed phase change material layer 150 is easy to be peeled off due to the shear stress of the planarization process. In order to avoid peeling off the formed phase change material layer, the downward force in the planarization process has to be small, and thus more polishing time is needed to remove a bulk phase change material layer, which results in poor uniformity and very limited process window of the planarization process.
In addition, when forming the phase change material layer 150 on the insulating layer 120 (referring to FIG. 2A), if the formed phase change material layer 150 is thick, it is easy to be peeled off. The peeling off of the formed phase change material layer not only decreases the productivity of devices, but also reduces the lifetime of dummy wafers (wafers that are processed during manufacturing but are not used for devices), which results in increase of the manufacturing cost.